Frontier: When Time Stands StillNews From The Frontier

That slow-motion sensation that often accompanies a situation that is life-threatening or otherwise high-adrenaline may be more than a sensation. It may be the brain's way of ensuring that we process every detail from all of our sensory channels in order to take the right action.

Scientists have uncovered evidence that the brain processes time subjectively according to the demands of the situation and uses different networks of cells to process information presented at different time points within the range of a second.

"Our perception of time is highly biased and flexible, depending on the motivational relevance and on our ability to orient our attention," argues Anna Nobre, a neuroscientist from Oxford University who has found "hot spots" for temporal processing on functional brain imaging scans.

Peter Tse, a neuropsychologist at Dartmouth College, has data suggesting that our "sense of time seems to expand when a strange event happens that attracts our attention." Just as not paying attention may lead us to under-estimate how much time has passed- think of being engrossed in a book and suddenly realizing it is 3 a.m.-attending to something closely may trigger our brains to subjectively stretch time.

"Attention can enhance temporal processing by making events be processed more slowly," Tse says. Such a strategy would make sense from an evolutionary standpoint, he argues, because "when it's life or death, we need more time to process what's going on."

Neurobiologist David Eagleman of the University of Texas, Houston, took the question of whether the brain can slow down time perception to an extreme. He got two volunteers to free fall 150 feet on a bungee cord with a palmtop computer strapped to their wrists and tested their ability to read numbers presented on the screen at a speed faster than a normal human can read. The novice jumpers had a much higher ability to read the numbers during the high-adrenaline rush of the free fall, which suggests that the brain can stretch out time under high-stress situations that demand our full attention.

Eagleman's group is seeking volunteers to continue his bungee-jumping studies.